package com.zhuandian.qxe.utils.MyView;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;

/**
 * 滚动选择器 
 *  
 * @author chenjing 
 *  
 */  
public class PickerView extends View
{  
  
    public static final String TAG = "PickerView";  
    /** 
     * text之间间距和minTextSize之比 
     */  
    public static final float MARGIN_ALPHA = 2.8f;  
    /** 
     * 自动回滚到中间的速度 
     */  
    public static final float SPEED = 2;  
  
    private List<String> mDataList;
    /** 
     * 选中的位置，这个位置是mDataList的中心位置，一直不变 
     */  
    private int mCurrentSelected;  
    private Paint mPaint;
  
    private float mMaxTextSize = 80;  
    private float mMinTextSize = 40;  
  
    private float mMaxTextAlpha = 255;  
    private float mMinTextAlpha = 120;  
  
    private int mColorText = 0x333333;  
  
    private int mViewHeight;  
    private int mViewWidth;  
  
    private float mLastDownY;  
    /** 
     * 滑动的距离 
     */  
    private float mMoveLen = 0;  
    private boolean isInit = false;  
    private onSelectListener mSelectListener;  
    private Timer timer;
    private MyTimerTask mTask;  
  
    Handler updateHandler = new Handler()
    {  
  
        @Override  
        public void handleMessage(Message msg)
        {  
            if (Math.abs(mMoveLen) < SPEED)  
            {  
                mMoveLen = 0;  
                if (mTask != null)  
                {  
                    mTask.cancel();  
                    mTask = null;  
                    performSelect();  
                }  
            } else  
                // 这里mMoveLen / Math.abs(mMoveLen)是为了保有mMoveLen的正负号，以实现上滚或下滚  
                mMoveLen = mMoveLen - mMoveLen / Math.abs(mMoveLen) * SPEED;  
            invalidate();  
        }  
  
    };  
  
    public PickerView(Context context)
    {  
        super(context);  
        init();  
    }  
  
    public PickerView(Context context, AttributeSet attrs)
    {  
        super(context, attrs);  
        init();  
    }  
  
    public void setOnSelectListener(onSelectListener listener)  
    {  
        mSelectListener = listener;  
    }  
  
    private void performSelect()  
    {  
        if (mSelectListener != null)  
            mSelectListener.onSelect(mDataList.get(mCurrentSelected));  
    }  
  
    public void setData(List<String> datas)  
    {  
        mDataList = datas;  
        mCurrentSelected = datas.size() / 2;  
        invalidate();  
    }  
  
    public void setSelected(int selected)  
    {  
        mCurrentSelected = selected;  
    }  
  
    private void moveHeadToTail()  
    {  
        String head = mDataList.get(0);  
        mDataList.remove(0);  
        mDataList.add(head);  
    }  
  
    private void moveTailToHead()  
    {  
        String tail = mDataList.get(mDataList.size() - 1);  
        mDataList.remove(mDataList.size() - 1);  
        mDataList.add(0, tail);  
    }  
  
    @Override  
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)  
    {  
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);  
        mViewHeight = getMeasuredHeight();  
        mViewWidth = getMeasuredWidth();  
        // 按照View的高度计算字体大小  
        mMaxTextSize = mViewHeight / 4.0f;  
        mMinTextSize = mMaxTextSize / 2f;  
        isInit = true;  
        invalidate();  
    }  
  
    private void init()  
    {  
        timer = new Timer();  
        mDataList = new ArrayList<String>();
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);  
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setTextAlign(Paint.Align.CENTER);
        mPaint.setColor(mColorText);  
    }  
  
    @Override  
    protected void onDraw(Canvas canvas)
    {  
        super.onDraw(canvas);  
        // 根据index绘制view  
        if (isInit)  
            drawData(canvas);  
    }  
  
    private void drawData(Canvas canvas)  
    {  
        // 先绘制选中的text再往上往下绘制其余的text  
        float scale = parabola(mViewHeight / 4.0f, mMoveLen);  
        float size = (mMaxTextSize - mMinTextSize) * scale + mMinTextSize;  
        mPaint.setTextSize(size);  
        mPaint.setAlpha((int) ((mMaxTextAlpha - mMinTextAlpha) * scale + mMinTextAlpha));  
        // text居中绘制，注意baseline的计算才能达到居中，y值是text中心坐标  
        float x = (float) (mViewWidth / 2.0);  
        float y = (float) (mViewHeight / 2.0 + mMoveLen);  
        Paint.FontMetricsInt fmi = mPaint.getFontMetricsInt();
        float baseline = (float) (y - (fmi.bottom / 2.0 + fmi.top / 2.0));  
  
        canvas.drawText(mDataList.get(mCurrentSelected), x, baseline, mPaint);  
        // 绘制上方data  
        for (int i = 1; (mCurrentSelected - i) >= 0; i++)  
        {  
            drawOtherText(canvas, i, -1);  
        }  
        // 绘制下方data  
        for (int i = 1; (mCurrentSelected + i) < mDataList.size(); i++)  
        {  
            drawOtherText(canvas, i, 1);  
        }  
  
    }  
  
    /** 
     * @param canvas 
     * @param position 
     *            距离mCurrentSelected的差值 
     * @param type 
     *            1表示向下绘制，-1表示向上绘制 
     */  
    private void drawOtherText(Canvas canvas, int position, int type)  
    {  
        float d = (float) (MARGIN_ALPHA * mMinTextSize * position + type  
                * mMoveLen);  
        float scale = parabola(mViewHeight / 4.0f, d);  
        float size = (mMaxTextSize - mMinTextSize) * scale + mMinTextSize;  
        mPaint.setTextSize(size);  
        mPaint.setAlpha((int) ((mMaxTextAlpha - mMinTextAlpha) * scale + mMinTextAlpha));  
        float y = (float) (mViewHeight / 2.0 + type * d);  
        Paint.FontMetricsInt fmi = mPaint.getFontMetricsInt();
        float baseline = (float) (y - (fmi.bottom / 2.0 + fmi.top / 2.0));  
        canvas.drawText(mDataList.get(mCurrentSelected + type * position),  
                (float) (mViewWidth / 2.0), baseline, mPaint);  
    }  
  
    /** 
     * 抛物线 
     *  
     * @param zero 
     *            零点坐标 
     * @param x 
     *            偏移量 
     * @return scale 
     */  
    private float parabola(float zero, float x)  
    {  
        float f = (float) (1 - Math.pow(x / zero, 2));  
        return f < 0 ? 0 : f;  
    }  
  
    @Override  
    public boolean onTouchEvent(MotionEvent event)
    {  
        switch (event.getActionMasked())  
        {  
        case MotionEvent.ACTION_DOWN:  
            doDown(event);  
            break;  
        case MotionEvent.ACTION_MOVE:  
            doMove(event);  
            break;  
        case MotionEvent.ACTION_UP:  
            doUp(event);  
            break;  
        }  
        return true;  
    }  
  
    private void doDown(MotionEvent event)  
    {  
        if (mTask != null)  
        {  
            mTask.cancel();  
            mTask = null;  
        }  
        mLastDownY = event.getY();  
    }  
  
    private void doMove(MotionEvent event)  
    {  
  
        mMoveLen += (event.getY() - mLastDownY);  
  
        if (mMoveLen > MARGIN_ALPHA * mMinTextSize / 2)  
        {  
            // 往下滑超过离开距离  
            moveTailToHead();  
            mMoveLen = mMoveLen - MARGIN_ALPHA * mMinTextSize;  
        } else if (mMoveLen < -MARGIN_ALPHA * mMinTextSize / 2)  
        {  
            // 往上滑超过离开距离  
            moveHeadToTail();  
            mMoveLen = mMoveLen + MARGIN_ALPHA * mMinTextSize;  
        }  
  
        mLastDownY = event.getY();  
        invalidate();  
    }  
  
    private void doUp(MotionEvent event)  
    {  
        // 抬起手后mCurrentSelected的位置由当前位置move到中间选中位置  
        if (Math.abs(mMoveLen) < 0.0001)  
        {  
            mMoveLen = 0;  
            return;  
        }  
        if (mTask != null)  
        {  
            mTask.cancel();  
            mTask = null;  
        }  
        mTask = new MyTimerTask(updateHandler);  
        timer.schedule(mTask, 0, 10);  
    }  
  
    class MyTimerTask extends TimerTask
    {  
        Handler handler;  
  
        public MyTimerTask(Handler handler)  
        {  
            this.handler = handler;  
        }  
  
        @Override  
        public void run()  
        {  
            handler.sendMessage(handler.obtainMessage());  
        }  
  
    }  
  
    public interface onSelectListener  
    {  
        void onSelect(String text);  
    }  
}  